Method to frost the inner surface of a glass bulb for electric lamps



April 9, 1935. 1-; NAIQQUSE 1,997,315,

METHOD TO FROST THE INNER SURFACE OF A GLASS BULB FOR ELECTRIC LAMPS Filed March 21, 1933 1 INVENTOR.' 77% 3a.

, BYf S 7% g q;

A TTORNEYS.

Patented Apr. 9, 1935 UNITED STATES METHOD TO FROST THE INNER SURFACE OF A GLASS BULB FOR ELECTRIC LAMPS Tomisaburo Naruse, Uchiyamashita-Oho,

Kojimachi-Ku, Tokyo, Japan Application March 21,

4 Claims.

This invention relates to a method to frost the inner surface of a glass bulb for electric lamp, characterized by the fact that first injecting and then extracting in the bulb through a narrow tube a corrosive liquid containing some powder having a lower specific gravity than that of any of the other elements of the corrosive liquid.

The purpose of this invention is to obtain the beautiful electric lamp bulbs having a uniformly frosted surface and having the gradually lessened frosted edge, instead of a sharp clear edge.

The accompanying drawing illustrates the method of the present invention.

Fig. 1 shows the state of the corroding liquid in the bulb, when the injecting action is finished.

Fig. 2 shows the frosted inner surface.

The glass bulb (a) is placed with the opening uppermost and through a narrow tube (b) is first injected into the bulb, the corroding liquid containing some powder, for example parafiin powder, wooden powder etc., having a lower specific gravity than that of any other element of the corroding liquid. The corroding mixture is subsequently extracted from the bulb.

In order that the invention may be fully un :ierstood, one practical example is given below:

Percent Hydrogen fluoride 38 Ammonium fluoride 38 Sulphuric aci 5 Water 15 1933, Serial No. 661,959

able apparatus, 50 both the powder and the liquid areinjected in the bulb also.

The powder in the bulb floats up from the bottom of the bulb, and this floating motion of the powder mixes it with the liquid in the bulb. Thus, the well mixed powder and liquid frosts the bulb uniformily, as shown in Fig. 2 (f) Then, when the'fioating motion of the greater part of the powder is finished, the surface of the liquid is covered with the accumulation of powder to some depth. The corroding action is lessened on the glass surface by said powder accumulation.

Thus, the edge line of the frosted surface is not sharp, but the degree of frosting is gradually lessened upwards as at (e).

Thus, beautiful electric lamp bulbs are obtained by this method.

I claim:

1. A method to frost the inner surface of'a glass bulb for electric lamp, consisting of first injecting into the. bulb a corrosive liquid containing an admixture of powder having a lower specific gravity than that of any of the other elements of the corrosive liquid and finally extracting said liquid from the bulb.

2. A method according to claim 1, in which said admixture consists of wood powder.

3. A method according to claim 1 in which said corrosive liquid comprises 38% hydrogen fluoride 38% ammonium fluoride, sulphuric acid and 15% water, all approximate proportions.

4. A method according to claim 1 in which said TOMISABURO NARUSE. 

